The term green roof refers to a roof that has been designed or modified to promote the intentional growth of plants on plant growth medium placed on the roof. In a typical construction, the existing roof structure has roofing material thereon, such as composition shingles, water impermeable membranes, or other roofing material. A water permeable roof protection layer, such as of a heavy duty fabric, is placed over the roof material to protect the roof material. A drainage layer, which may comprise, for example, aggregate or a drainage mat, is positioned over the roof protection layer to facilitate the passage of rain water off of the roof. A root barrier layer overlies the drainage layer to prevent plant roots from growing into the drainage layer wherein the roots could otherwise clog the drainage area. Plant growth medium is then supported above the root barrier layer with plants forming the green roof growing in the plant growth medium.
There are a number of advantages to green roofs. For example, green roofs retard storm water run-off. As a result, water retained on the roof can evaporate instead of running immediately off the roof where it is typically collected in storm drains. This run-off water can contain pollutants washed by the rain water from streets and other sources. Therefore, a reduction in run-off water reduces the amount of pollutant laden water that reenters streams or that is treated before being passed on. In addition, green roofs provide an added insulation factor that reduces the amount of energy required to heat or cool a home or other structure having the green roof. In addition, green roofs can enhance the life of a roof by shielding the roof from ultraviolet ray exposure and from temperature effects, such as arising from freezing and thawing cycles in many climates.
Given the many advantages of green roofs, they are becoming more and more popular. Therefore, a need exists for improved green roofs, components for such roofs, and related methods.